In the prior art, there has been developed an implement commonly referred to as a "thumb" mountable on the underside of the handle of an excavating machine which is operable independently to perform various work functions or in cooperation with the bucket of the machine for grasping material between the thumb and the bucket. Typically, the thumb is fixed relative to the handle of the machine and the bucket may be curled and uncurled to grasp material being handled. The thumb also is usually connected to the handle with a strut which may be either of a fixed or extendable length to permit adjustment of the angle of the thumb relative to the handle. The strut may consist of a rigid link detachably securable to one of a number of brackets disposed on the underside of the handle or a hydraulic cylinder assembly, the length of which may be varied between a fully extended position, a fully retracted or stored position adjacent the underside of the handle or a position therebetween.
In such an arrangement, it is desirable to be able to readily retract the thumb to the storage position to permit the bucket to be operated independent of the thumb, reliably secure the thumb in the storage position while the bucket is being operated, quickly and easily release the thumb and readily reposition it to a desired angle relative to the handle to cooperate with the bucket to perform material handling operations. It further is desirable to be able to reposition the thumb between selected operable positions and the storage position and to lock and release the thumb in the storage position, from the operator's station on the machine. It thus is the principal object of the present invention to provide such an assembly which may be operated in the manner described.